Carl Jantz, the originator of the patent did a lot of research with different lubricants. This turned out to be the best. I have an email from him that explains his research but it's on my work computer. I'll look it up tomorrow.

Hello, my name is Carl Jantz and I designed and tested the super joint.
Iíd just like to set the record straight for those who think the Yukon super joint is just a cheap copy of other extreme joints on the market today. I have been working on a better U-joint since I broke my 1st front axle U-joint in 1978. After trying every brand, I eventually used Spicerís, but in the old bronco they were the 260x joints, eventually as tires got bigger and several U-joints later, I stumbled on the fact that some Dana 44s used 297x (now 760x) u-joints and bored out my axles to fit. Then of course the ears tore off or stretched, so I built them up with a stick welder and 7018 welding rod. This worked very well for years, then along came still bigger tires and extreme 4 wheeling. I looked at modifying Dana 60 crosses to fit into the D44 caps around 1985 but decided no one would be willing to pay the price of buying 2 U-joints and then machine work to make them work, plus brass bushings that would eventually deform under the extreme pressure exerted upon them. (I didnít know about beryllium bronze at that time). So I built my 1st Dana 60 5 lug front (1986) end and went happily 4 wheelin with 18/44ís for years. Then I went to the 1st NWRCA rock crawl at Vantage Washington and realized that there was a real need for a stronger joint and that a few people would be willing to pay for them. By this time I had worked a Boeing in R & D and had worked with Ionic coatings to drill through Titanium. I figured if It made the drills last significantly longer and since NASCAR was using Ionic coatings on the ring and pinions with great success to reduce friction that they might work on the u-joint crosses to avoid using a bearing. To learn more about Ionic coatings to go to www.Ionbond.com. (Note Ford Model A cars used no needle bearings in their U joints, just 140wt grease and hardened caps on hardened crosses, but then they were only dealing with 40 hp.)
So I had a drill bushing company make some 4340 hardened bushings for me that press fit over the 297X crosses and fit into the caps to replace the needle bearings, and then set up a design of experiments to test various greases and Ionic coatings.
I first used one grease with several coatings to find the best Ionic coating. Then I used one Ionic coating to test several greases. The last test went something like this. Installed 2 Joints into front end of diesel suburban with 4 kinds of greases, one type of grease in 2 caps. Then I pulled out the rear drive line and with my jeep on the trailer behind the suburban went on a 1200 mile road trip including Stevens pass, Snoqualmie pass and White Pass. (Getting started in front wheel drive was a pain sometimes) I then inspected the joints and found out two things. All of the greases were just fine, AND there was water in the joints. Now this was all highway driving in 70 plus weather except one Ĺ hour rain storm, I figured out that as the cold water sprayed up on the u-joints they cooled down creating an internal suction that pulled the water inside the joints, hence they now have pressurized grease reservoirs.
So on to finally test the greases, I chained the rear end to a tree with the front end on dry pavement, and burned a set of tires to the cords in 45 minutes of smoke. All the greases failed except one, and it looked just like I had just assembled the joint and never tested it at all. The grease is an Aircraft spec anti-seize. All automotive greases, even the synthetics never even came close to this stuff.
So with parameters set it was time to combine all factors and do a real world test. 16 joints were made from billet and tested at Cedar City in the April of 2002 at the U-roc crawl. There were no failures and, all of the rigs using the joints placed in the top ten at the event. So onto production, attaining a patent and working with a distributor, and now they are finally here. We really worked on having a product that gives superior performance at a reasonable price. If you would like to see a little more please visit my website for an install. www.jantz4x4.com